Semi-Flex Component Carrier With Dielectric Material Having High Elongation and Low Young Modulus

ABSTRACT

A semi-flex component carrier includes a stack having at least one electrically insulating layer structure, at least one electrically conductive layer structure and a stress propagation inhibiting barrier. The stack defines at least one rigid portion and at least one semi-flexible portion. The stress propagation inhibiting barrier includes a plurality of stacked vias filled at least partially with electrically conductive material in an interface region between the at least one rigid portion and the at least one semi-flexible portion and configured to inhibit stress propagation between the at least one rigid portion and the at least one semi-flexible portion during bending.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/947,417 and claims priority to China Patent Application No.20191072769.5 filed Aug. 6, 2019, the disclosures of which are herebyincorporated herein by reference.

TECHNICAL FIELD

The invention relates to a semi-flex component carrier and a method ofmanufacturing a semi-flex component carrier.

TECHNOLOGICAL BACKGROUND

In the context of growing product functionalities of component carriersequipped with one or more electronic components and increasingminiaturization of such components as well as a rising number ofcomponents to be mounted on the component carriers such as printedcircuit boards, increasingly more powerful array-like components orpackages having several components are being employed, which have aplurality of contacts or connections, with ever smaller spacing betweenthese contacts. Removal of heat generated by such components and thecomponent carrier itself during operation becomes an increasing issue.At the same time, component carriers shall be mechanically robust andelectrically reliable so as to be operable even under harsh conditions.

Different types of partially flexible and partially rigid componentcarriers exist. A “rigid-flex component carrier” comprises a fullyflexible portion, for instance made of polyimide, being a differentmaterial than stiffer dielectric material of a rigid portion. However,implementing fully flexible materials such as polyimide in a componentcarrier is cumbersome and involves reliability issues.

Another conventional type of partially flexible and partially rigidcomponent carriers is a “semi-flex component carrier” which is acomponent carrier in which its semi-flexible portion may comprise thesame dielectric (for instance FR4) material as a rigid portion, so thatbendability of the semi-flexible portion only results from the reducedthickness in the semi-flexible region. However, conventional semi-flexcomponent carriers are prone to breakage upon bending a semi-flexibleportion thereof.

SUMMARY

There may be a need to provide a partially rigid and partially flexiblecomponent carrier with high reliability.

According to an exemplary embodiment of the invention, a semi-flexcomponent carrier is provided which comprises a stack (in particular alaminated stack, i.e. a stack in which its layer structures areconnected by the application of heat and/or pressure) comprising atleast one electrically insulating layer structure and/or at least oneelectrically conductive layer structure, wherein the stack defines atleast one rigid portion and at least one semi-flexible portion, whereinat least one of the at least one electrically insulating layer structureforming at least part of the semi-flexible portion comprises a materialhaving an elongation of larger than 3% (in particular at a temperatureof 300 K) and a Young modulus of less than 5 GPa (in particular at atemperature of 300 K).

According to another exemplary embodiment of the invention, a method ofmanufacturing a semi-flex component carrier is provided, wherein themethod comprises providing (in particular laminating, i.e. connecting bythe application of heat and/or pressure) a stack comprising at least oneelectrically insulating layer structure and/or at least one electricallyconductive layer structure, wherein the stack defines at least one rigidportion and at least one semi-flexible portion, and forming at least oneof the at least one electrically insulating layer structure forming atleast part of the semi-flexible portion from a material having anelongation of larger than 3% (in particular at a temperature of 300 K)and a Young modulus of less than 5 GPa (in particular at a temperatureof 300 K).

A semi-flex component carrier having a stack, in particular a laminatedstack, with at least one electrically insulating layer structure, atleast one electrically conductive layer structure and a stresspropagation inhibiting barrier. The stack defines at least one rigidportion and at least one semi-flexible portion. In an interface regionbetween the at least one rigid portion and the at least onesemi-flexible portion, the stress propagation inhibiting barrierincludes a plurality of stacked vias filled at least partially withelectrically conductive material and configured to inhibit stresspropagation between the at least one rigid portion and the at least onesemi-flexible portion during bending.

A method of manufacturing a semi-flex component carrier includesproviding, in particular laminating, a stack having at least oneelectrically insulating layer structure, at least one electricallyconductive layer structure, and a stress propagation inhibiting barrier,wherein the stack defines at least one rigid portion and at least onesemi-flexible portion. In an interface region between the at least onerigid portion and the at least one semi-flexible portion, the stresspropagation inhibiting barrier includes a plurality of stacked viasfilled at least partially with electrically conductive material andconfigured to inhibit stress propagation between the at least one rigidportion and the at least one semi-flexible portion during bending.

OVERVIEW OF EMBODIMENTS

In the context of the present application, the term “component carrier”may particularly denote any support structure which is capable ofaccommodating one or more components thereon and/or therein forproviding mechanical support and/or electrical connectivity. In otherwords, a component carrier may be configured as a mechanical and/orelectronic carrier for components. In particular, a component carriermay be one of a printed circuit board, an organic interposer, and an IC(integrated circuit) substrate. A component carrier may also be a hybridboard combining different ones of the above-mentioned types of componentcarriers.

In the context of the present application, the term “rigid portion” mayparticularly denote a portion of the component carrier which, whenapplying or exerting ordinary forces typically occurring duringoperation of the component carrier, the rigid portion will remainsubstantially undeformed. In other words, the shape of the rigid portionwill not be changed when applying forces during operation of thecomponent carrier.

In the context of the present application, the term “semi-flexibleportion” may particularly denote a portion of the component carrierwhich, upon exerting typical forces occurring during operation of thecomponent carrier, may result in a deformation of the semi-flexibleportion. The deformation of the semi-flexible portion may be possible tosuch an extent that the shape of the entire component carrier may besignificantly influenced by deforming the semi-flexible portion.However, such a semi-flexible portion may be less flexible than a fullyflexible portion (formed, for instance, from polyimide). Bending of thesemi-flexible portion without breakage may be possible only once, only alimited number of bending cycles, or may be even possible without damagefor an infinite number of bending cycles.

In the context of the present application, the term “semi-flex componentcarrier with semi-flexible portion” may particularly denote a componentcarrier in which its semi-flexible portion may be made, partially orentirely, of the same dielectric and/or metallic material as one or moreadjacent rigid portions, but may for instance only have a locallysmaller thickness than the connected rigid portion(s). In such aconfiguration, bendability of the semi-flexible portion only resultsfrom the reduced thickness rather than from a more flexible material inthe flexible portion. In contrast to such a semi-flex component carrier,a rigid-flex component carrier (i.e. another type of partially flexibleand partially rigid component carrier) comprises a fully flexibleportion, for instance made of polyimide (for example having anelongation of about 70%). In such an embodiment, the material of theflexible portion may be different from the material of one or twoadjacent rigid portions, and the material of the flexible portion may bespecifically selected to have high elasticity or flexibility.

In the context of the present application, the term “Young modulus” mayparticularly denote the elastic modulus, i.e. a measure of the stiffnessof a solid material and defines the relationship between stress (forceper unit area) and strain (proportional deformation) in a material. Asofter material has a smaller value of the Young modulus than a morerigid material.

In the context of the present application, the term “elongation”,“percent elongation” or “percentage elongation” may particularly denotea remaining elongation of a body after breakage in relation to itsinitial length. Percent elongation may be a measurement that capturesthe amount a material will plastically and/or elastically deform up tofracture. Percent elongation is one way to measure and quantifyductility of a material. The material's final length may be comparedwith its original length to determine the percent elongation and thematerial's ductility. To calculate percent elongation, the originallength of a gauge span may be subtracted from the final length. Then theresult from that subtraction may be divided by the original length andmultiplied by 100 to obtain the percent elongation. The equation is:elongation=100×[(final length−initial length)/initial length].Elongation is hence indicative of the ductility of a material. Amaterial with a higher elongation is a more ductile material, while amaterial with a lower percentage will be more brittle. For instance, FR4may have an elongation of about 1-2%.

According to an exemplary embodiment of the invention, a semi-flexcomponent carrier is provided which comprises a dielectric material atleast in a semi-flexible portion thereof and having a combination of aYoung modulus (i.e. a ratio between an expanding force and a spatialexpansion) of less than 5 GPa and an elongation (i.e. a relative lengthexpansion at a point of failure) of more than 3%. Descriptivelyspeaking, such a dielectric material in a semi-flexible portion of asemi-flex component carrier has a higher elasticity and is more ductilethan conventional FR4 material. As a result, the semi-flex componentcarrier may be less prone to failure (in particular less prone to theformation of cracks or to breakage) when the semi-flexible portion isbent.

Thus, an exemplary embodiment of the invention applies a low modulusmaterial with high elongation or ultimate strain on a semi-flexcomponent carrier such as a semi-flex printed circuit board (PCB). As aresult, it may be advantageously possible to realize a semi-flexcomponent carrier with a small bending radius and/or an increased number(for instance at least two or at least three) of flexible layers in asemi-flexible portion of the component carrier. Thus, exemplaryembodiments of the invention may make it possible to solve issues withconventional semi-flex applications. In contrast to conventionalapproaches, in which standard PCB materials are applied on the bend areaof a semi-flex component carrier for the usage of standard HDI (highdensity interconnect) and/or mSAP (modified semi-additive processing)PCB (printed circuit board) design rules to avoid limitations withpolyimide rigid-flex technology, exemplary embodiments of the inventionsynergistically implement dielectric material with a Young modulus ofless than 5 GPa and a percent elongation of more than 3%. By taking thismeasure, significant vulnerabilities of conventionally used dielectricmaterial in the semi-flexible portion of a semi-flex component carriercan be over-come. Based on simulations, the described solution has beenidentified which shows particularly advantageous properties when usinglow or even ultra-low Young modulus materials in combination with aspecifically selected range of ductility. While conventionalsemi-flexible PCBs have been used for high bend radius applications onlywith an estimated radius of for example more than 5 mm up to 5 cyclebending requirement, exemplary embodiments of the invention maysignificantly lower the bend radius, for instance down to 2 mm, and/ormay increase the bending endurance up to 100 cycles with larger bendingcondition (for instance larger than 5 mm).

In the following, further exemplary embodiments of the method and thecomponent carrier will be explained.

In an embodiment, the at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion comprises or consists of a resin, in particular an epoxy resin.In particular, a proper selection of the base resin and/or one or moreadditives may allow to adjust the properties of said dielectric layer interms of elasticity/Young modulus and ductility/elongation.

In an embodiment, the at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion comprises epoxy derivatives, in particular Ajinomoto Build-upFilm®. Ajinomoto Build-Up Film is a registered trademark of AjinomotoCo., Inc. of Tokyo, Japan. Such a material may be a suitable choice toprovide the above-described properties in terms of low Young modulus andhigh elongation.

In an embodiment, the at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion is free of glass cloth. The omission of glass fibers, glassspheres or any other reinforcing particles in a resin matrix of the atleast one electrically insulating layer structure with low Young modulusand high elongation may promote improved bendability in thesemi-flexible portion in view of the obtainable high elasticity and highductility.

In an embodiment, the at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion extends over the (in particular entire) at least onesemi-flexible portion and over the (in particular entire) at least onerigid portion. In other words, said dielectric layer with low Youngmodulus and high elongation may be shared between the semi-flexibleportion and the rigid portion(s) of the component carrier. Forming saiddielectric layer with low Young modulus and high elongation over boththe semi-flexible portion and the at least one rigid portion may preventmechanical weak points at one or more material inter-faces between thesemi-flexible portion and one or more rigid portions. Such materialinterfaces may result from different materials of the dielectric in saidportions and can be avoided by extending at least one continuoushomogeneous dielectric layer with low Young modulus and high elongationextending over the entire horizontal expansion of the component carrier.Such a homogeneous dielectric layer may also be advantageous to suppressCTE (coefficient of thermal expansion) mismatch.

In an embodiment, the at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion is the outermost electrically insulating layer structure of thestack. Simulations have shown that in particular the outermostdielectric layer of the semi-flex component carrier is prone to failureduring bending and suffers from the largest mechanical load in thesemi-flexible portion and at its interface(s) to the rigid portion(s)during bending. The outermost dielectric layer of the semi-flexcomponent carrier may experience maximum stretching during bending, sothat the formation of said dielectric layer with the low value of theYoung modulus and the high value of the elongation is in particularadvantageous to prevent cracks during bending.

Additionally or alternatively, a dielectric layer with low Young modulusand high elongation forming at least part of the semi-flexible portionmay be located in an interior, in particular at a center, of theelectrically insulating layer structures of the stack. While thevertical center of the semi-flexible portion is usually less prone tofailure than the outermost portion, configuring a central dielectriclayer of the semi-flexible portion from a material with low Youngmodulus and high elongation can nevertheless support bendability indesigns in which the outermost dielectric layer should be made ofanother material (for instance should comprise glass cloth for stabilityreasons). Highly advantageously, more than one layer structure (at leastin the semi-flexible portion) may be made of a material having a lowYoung modulus and high elongation. In particular the provision of boththe outer-most as well as a central dielectric layer structure of amaterial having low Young modulus and high elongation may be highlyadvantageous.

In an embodiment, all of the layer structures of the semi-flexibleportion also extend along the at least one rigid portion. Highlyadvantageously, both the electrically conductive layer structures (inparticular made of copper) as well as the electrically insulating layerstructures (for instance comprising prepreg, FR4 and/or a material withlow Young modulus and high elongation) of the semi-flexible portion mayalso extend into the one or more connected rigid portions. This ensuresa high homogeneity and a high mechanical robustness of the componentcarrier as a whole. In particular, all of the layer structures are madeof the same material and/or have the same thickness in the semi-flexibleportion and in the at least one rigid portion. By taking this measure,the homogeneity of the semi-flexible portion and the connected regionsof the one or more rigid portions may be further enhanced.

In an embodiment, the component carrier has a semi-flexible portionbetween two opposing rigid portions. Alternatively, it is however alsopossible that the semi-flexible portion is connected at one side to arigid portion, whereas its opposing other side is unconnected.

In an embodiment, the at least one semi-flexible portion has a smallernumber of layer structures and/or has a smaller thickness than the atleast one rigid portion. Correspondingly, a cavity may be formed aboveand/or below the semi-flexible portion corresponding to layer structuresof the connected rigid portion which are lacking in the semi-flexibleportion.

In an embodiment, the at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion comprises a polymer having a flexible segment between a reactivesegment and a hard segment. In particular, the hard segment may have ahigh temperature resistance, the flexible segment may show low warpageand relaxation on internal stress, and/or the reactive segment may beconfigured for reacting with epoxy resin. Descriptively speaking, thehard segment may have a high temperature resistance. The reactivesegment may be capable of reacting with epoxy resin, for instance bycross-linking and/or by the formation of chemical bonds. The flexiblesegment in between may function as a flexible binder showing a lowwarpage and promoting relaxation on internal stress. By using such apolymer for the at least one electrically insulating layer structurewith low Young modulus and high elongation, the proper bendability andhigh mechanical stability of the component carrier may be furtherimproved.

In an embodiment, at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion has a Young modulus of less than 2 GPa, in particular less than1 GPa (in particular at a temperature of 300 K). By taking this measure,the elasticity of the semi-flexible portion may be further enhanced, andthe risk of failure during bending may be further suppressed.

In an embodiment, at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion has an elongation of larger than 4%, in particular larger than5%, more particularly larger than 10% (in particular at a temperature of300 K). Such a material in the semi-flexible portion may further promoteductility of the dielectric material and may improve mechanicalintegrity of the component carrier, even in the presence of smallbending angles.

Furthermore, said material preferably has an elongation of less than 20%(in particular at a temperature of 300 K) in order to prevent excessiveflexibility or bendability of the rigid portion (into which saiddielectric layer may extend). An excessive elongation might deterioratethe mechanical stability of the component carrier as a whole.

In an embodiment, at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion has a coefficient of thermal expansion of less than 150 ppm/K ata temperature of 300 K. At the same time, it may be advantageous if thethermal expansion is at least 30 ppm/K. By correspondingly configuringthe material of said dielectric layer structure, thermal stress withinthe component carrier can be suppressed even in the presence ofpronounced temperature cycles.

In an embodiment, the semi-flexible portion has a horizontal length ofat least 1 mm. By fulfilling this design rule, bendability of thesemi-flexible portion may be further increased while keeping the risk ofcrack formation or the like during bending small.

In an embodiment, at least one of the at least one electricallyinsulating layer structure forming at least part of the semi-flexibleportion is bent about a bending angle in a range between 0° in 180°. Forinstance, bending may occur with a bending angle in a range between 60°and 160° without the risk of failure.

In an embodiment, said at least one electrically insulating layerstructure with low Young modulus below 5 GPa and high elongation above3% is laminated as part of a resin coated copper (RCC) foil to the restof the stack. This lamination may be accomplished in particular both inthe semi-flexible portion and in the at least one rigid portion. In thecontext of the present application, the term “RCC” may particularlydenote a double layer (or multilayer) having a copper foil with a mainsurface on which a resin film is applied. Such a resin film of aseparate RCC foil may be at least partially uncured or may be alreadyfully cured before connection with the other layer structures of thestack so that the RCC foil can be laminated as a whole to a layer stack.This simplifies handling and thus simplifies the manufacturing processof the component carrier. As a result, the RCC foil and thus also saidat least one electrically insulating layer structure with low Youngmodulus below 5 GPa and high elongation above 3% may extend in an entirehorizontal plane of the component carrier to be manufactured, i.e. maybe present both in the semi-flexible portion and in the at least onerigid portion. This results in a homogeneous material distribution overthe entire component carrier and thus suppresses undesired CTE mismatchwhich may result from inhomogeneous material distribution over thecomponent carrier.

In an embodiment, the component carrier comprises a stress propagationinhibiting barrier (in particular a plurality of stacked vias filled atleast partially with electrically conductive material) in an interfaceregion between the at least one rigid portion and the at least onesemi-flexible portion and configured for inhibiting stress propagationbetween the at least one rigid portion and the at least onesemi-flexible portion during bending. Descriptively speaking, thementioned stress propagation inhibiting barrier may be arranged totraverse a stress propagation trajectory between the at least one rigidportion and the at least one semi-flexible portion (in particular from abending point to an embedded component) and may thus function forpreventing propagation of bending stress.

In an embodiment, a transition region between the at least one rigidportion and the at least one semi-flexible portion has at least oneslanted sidewall. A slanted sidewall at a bending position has turnedout to reduce stress propagation within the component carrier.

In an embodiment, at least one component may be embedded in thepartially flexible and partially rigid component carrier, in particularin a rigid portion thereof. In another embodiment, at least onecomponent may also be embedded in the semi-flexible portion of such apartially flexible and partially rigid component carrier. Additionallyor alternatively, at least one component may be surface mounted on thepartially flexible and partially rigid component carrier, in particularon a rigid portion thereof. It is also possible that at least onecomponent is surface mounted on a semi-flexible portion of such acomponent carrier.

In an embodiment, the component carrier may comprise a mechanical bufferstructure surrounding at least part of the (in particular embedded)component and having a lower value of the Young modulus than otherelectrically insulating material of the stack. In particular, thecomponent may be embedded in a core of the at least one rigid portion,and at least one electrically insulating layer structure of the stacksurrounding at least part of the component may have a lower Youngmodulus than electrically insulating material of the core. According tosuch an embodiment, a semi-flex component carrier is provided whichcomprises a mechanical buffer structure as dielectric material at leastpartly encapsulating a component embedded in the stack, in particular inthe rigid portion. Said mechanical buffer structure may have a value ofthe Young modulus (i.e. a ratio between an expanding force and a spatialexpansion) being smaller than that of at least part of surroundingelectrically insulating material of the stack. Descriptively speaking,such a dielectric material partially or entirely surrounding a componentembedded in a semi-flex component carrier has a higher elasticity thanother dielectric material of the stack, for instance made of FR4material. As a result, the semi-flex component carrier may be less proneto failure (in particular less prone to the formation of cracks or tobreakage) in particular in a volume portion corresponding to theembedded component when the semi-flexible portion is bent. Hence, acomponent carrier configured as a complete package provided in embeddingtechnology may be combined with semi-flex technology. By taking thesemeasures, a semi-flexible (in particular non-polyimide) based componentcarrier with embedded component and with semi-flex characteristics maybe configured to be robust against bending stress.

In an embodiment, the mechanical buffer structure comprises a materialhaving an elongation of larger than 3%, in particular larger than 5%,and a Young modulus of less than 5 GPa, in particular less than 1 GPa.Descriptively speaking, such a dielectric material of the mechanicalbuffer structure may have a higher elasticity and may be more ductilethan conventional FR4 material. As a result, the embedded component maybe less prone to failure (in particular less prone to the formation ofcracks or to breakage) when the semi-flexible portion is bent.

In an embodiment, a vertical extension range of the component does notencompass a vertical level of at least one bending point between the atleast one rigid portion and the at least one semi-flexible portion. Byarranging the embedded component at a vertical height different from avertical position of a bending between the semi-flexible portion and therigid portion, the robustness of the embedded component encapsulated inthe mechanical buffer structure can be further increased.

The one or more components can be selected from a group consisting of anelectrically non-conductive inlay, an electrically conductive inlay(such as a metal inlay, preferably comprising copper or aluminum), aheat transfer unit (for example a heat pipe), a light guiding element(for example an optical waveguide or a light conductor connection), anelectronic component, or combinations thereof. For example, thecomponent can be an active electronic component, a passive electroniccomponent, an electronic chip, a storage device (for instance a DRAM oranother data memory), a filter, an integrated circuit, a signalprocessing component, a power management component, an optoelectronicinterface element, a voltage converter (for example a DC/DC converter oran AC/DC converter), a cryptographic component, a transmitter and/orreceiver, an electromechanical transducer, a sensor, an actuator, amicroelectromechanical system (MEMS), a microprocessor, a capacitor, aresistor, an inductance, a battery, a switch, a camera, an antenna, alogic chip, a light guide, and an energy harvesting unit. However, othercomponents may be embedded in the component carrier. For example, amagnetic element can be used as a component. Such a magnetic element maybe a permanent magnetic element (such as a ferromagnetic element, anantiferromagnetic element or a ferrimagnetic element, for instance aferrite base structure) or may be a paramagnetic element. However, thecomponent may also be a further component carrier, for example in aboard-in-board configuration. One or more components may be surfacemounted on the component carrier and/or may be embedded in an interiorthereof. Moreover, also other than the mentioned components may be usedas component.

In an embodiment, the component carrier comprises a stack of at leastone electrically insulating layer structure and at least oneelectrically conductive layer structure. For example, the componentcarrier may be a laminate of the mentioned electrically insulating layerstructure(s) and electrically conductive layer structure(s), inparticular formed by applying mechanical pressure, if desired supportedby thermal energy. The mentioned stack may provide a plate-shapedcomponent carrier capable of providing a large mounting surface forfurther components and being nevertheless very thin and compact. Theterm “layer structure” may particularly denote a continuous layer, apatterned layer or a plurality of non-consecutive islands within acommon plane.

In an embodiment, the component carrier is shaped as a plate. Thiscontributes to the compact design, wherein the component carriernevertheless provides a large basis for mounting components thereon.Furthermore, in particular a naked die as example for an embeddedelectronic component, can be conveniently embedded, thanks to its smallthickness, into a thin plate such as a printed circuit board.

In an embodiment, the component carrier is configured as one of thegroup consisting of a printed circuit board, and a substrate (inparticular an IC substrate).

In the context of the present application, the term “printed circuitboard” (PCB) may particularly denote a component carrier (which may beplate-shaped (i.e. planar), three-dimensionally curved (for instancewhen manufactured using 3D printing) or which may have any other shape)which is formed by laminating several electrically conductive layerstructures with several electrically insulating layer structures, forinstance by applying pressure, if desired accompanied by the supply ofthermal energy. As preferred materials for PCB technology, theelectrically conductive layer structures are made of copper, whereas theelectrically insulating layer structures may comprise resin and/or glassfibers, so-called prepreg or FR4 material. The various electricallyconductive layer structures may be connected to one another in a desiredway by forming through-holes through the laminate, for instance by laserdrilling or mechanical drilling, and by filling them with electricallyconductive material (in particular copper), thereby forming vias asthrough-hole connections. Apart from one or more components which may beembedded in a printed circuit board, a printed circuit board is usuallyconfigured for accommodating one or more components on one or bothopposing surfaces of the plate-shaped printed circuit board. They may beconnected to the respective main surface by soldering. A dielectric partof a PCB may be composed of resin with reinforcing fibers (such as glassfibers).

In the context of the present application, the term “substrate” mayparticularly denote a small component carrier having substantially thesame size as a component (in particular an electronic component) to bemounted thereon. More specifically, a substrate can be understood as acarrier for electrical connections or electrical networks as well ascomponent carrier comparable to a printed circuit board (PCB), howeverwith a considerably higher density of laterally and/or verticallyarranged connections. Lateral connections are for example conductivepaths, whereas vertical connections may be for example drill holes.These lateral and/or vertical connections are arranged within thesubstrate and can be used to provide electrical and/or mechanicalconnections of housed components or unhoused components (such as baredies), particularly of IC chips, with a printed circuit board orintermediate printed circuit board. Thus, the term “substrate” alsoincludes “IC substrates”. A dielectric part of a substrate may becomposed of resin with reinforcing spheres (such as glass spheres).

In an embodiment, dielectric material of at least one electricallyinsulating layer structure comprises at least one of the groupconsisting of resin (such as reinforced or non-reinforced resins, forinstance epoxy resin or Bismaleimide-Triazine resin, more specificallyFR-4 or FR-5), cyanate ester, polyphenylene derivate, glass (inparticular glass fibers, multi-layer glass, glass-like materials),prepreg material, epoxy-based Build-Up Film, polytetrafluoroethylene(Teflon®), a ceramic, and a metal oxide. Teflon is a registeredtrademark of The Chemours Company FC LLC of Wilmington, Del. U.S.A.Reinforcing materials such as webs, fibers or spheres, for example madeof glass (multilayer glass) may be used as well. Although prepreg or FR4are usually preferred, other materials may be used as well. For highfrequency applications, high-frequency materials such aspolytetrafluoroethylene, liquid crystal polymer and/or cyanate esterresins may be implemented in the component carrier as electricallyinsulating layer structure.

In an embodiment, electrically conductive material of the at least oneelectrically conductive layer structure comprises at least one of thegroup consisting of copper, aluminum, nickel, silver, gold, palladium,and tungsten. Although copper is usually preferred, other materials orcoated versions thereof are possible as well, in particular coated witha supra-conductive material such as graphene.

In an embodiment, the component carrier is a laminate-type body. In suchan embodiment, the semifinished product or the component carrier is acompound of multiple layer structures which are stacked and connectedtogether by applying a pressing force, if desired accompanied by heat.

After processing interior layer structures of the component carrier, itis possible to cover (in particular by lamination) one or both opposingmain surfaces of the processed layer structures symmetrically orasymmetrically with one or more further electrically insulating layerstructures and/or electrically conductive layer structures. In otherwords, a build-up may be continued until a desired number of layers isobtained.

After having completed formation of a stack of electrically insulatinglayer structures and electrically conductive layer structures, it ispossible to proceed with a surface treatment of the obtained layersstructures or component carrier.

In particular, an electrically insulating solder resist may be appliedto one or both opposing main surfaces of the layer stack or componentcarrier in terms of surface treatment. For instance, it is possible toform such as solder resist on an entire main surface and to subsequentlypattern the layer of solder resist so as to expose one or moreelectrically conductive surface portions which shall be used forelectrically coupling the component carrier to an electronic periphery.The surface portions of the component carrier remaining covered withsolder resist may be efficiently protected against oxidation orcorrosion, in particular surface portions containing copper.

It is also possible to apply a surface finish selectively to exposedelectrically conductive surface portions of the component carrier interms of surface treatment. Such a surface finish may be an electricallyconductive cover material on exposed electrically conductive layerstructures (such as pads, conductive tracks, etc., in particularcomprising or consisting of copper) on a surface of a component carrier.If such exposed electrically conductive layer structures are leftunprotected, then the exposed electrically conductive component carriermaterial (in particular copper) might oxidize, making the componentcarrier less reliable. A surface finish may then be formed for instanceas an interface between a surface mounted component and the componentcarrier. The surface finish has the function to protect the exposedelectrically conductive layer structures (in particular coppercircuitry) and enable a joining process with one or more components, forinstance by soldering. Examples for appropriate materials for a surfacefinish are OSP (Organic Solderability Preservative), Electroless NickelImmersion Gold (ENIG), gold (in particular Hard Gold), chemical tin,nickel-gold, nickel-palladium, etc.

The aspects defined above and further aspects of the invention areapparent from the examples of embodiment to be described hereinafter andare explained with reference to these examples of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5 illustrate cross-sectionalviews of structures obtained during manufacturing a component carrieraccording to an exemplary embodiment of the invention.

FIG. 6 illustrates a cross-sectional view of a component carrieraccording to another exemplary embodiment of the invention.

FIG. 7 illustrates a three-dimensional view of a component carrieraccording to still another exemplary embodiment of the invention.

FIG. 8 illustrates a design of a component carrier according to afurther exemplary embodiment of the invention.

FIG. 9 illustrates a cross-sectional view of a component carrieraccording to still another exemplary embodiment of the invention.

FIG. 10 illustrates a cross-sectional view of a component carrieraccording to yet another exemplary embodiment of the invention.

FIG. 11 illustrates a polymer with different functional sections usedaccording to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The illustrations in the drawings are schematic. In different drawings,similar or identical elements are provided with the same referencesigns.

Before, referring to the drawings, exemplary embodiments will bedescribed in further detail, some basic considerations will besummarized based on which exemplary embodiments of the invention havebeen developed.

Conventionally, standard PCB materials are applied on a bend area of asemi-flex component carrier to allow usage of standard HDI (high densityinterconnect) and/or mSAP (modified semi-additive processing) PCB designrules. In an alternative conventional approach, a highly flexiblematerial such as polyimide is applied in rigid-flex technology, whichhowever involves significant limitations due to the use of the polyimidematerial.

According to an exemplary embodiment of the invention, it is possible toapply a dielectric low modulus and high elongation material to asemi-flexible portion of a semi-flex component carrier (in particularprinted circuit board, PCB). This may allow to resolve a small bendingradius and enable a dynamic bending angle on a semi-flex componentcarrier. In particular, this may be achieved by configuring a dielectricmaterial at least in the semi-flexible portion to have a low Youngmodulus below 5 GPa and high elongation above 3%. Consequently, thedielectric material in the semi-flexible portion may be both elastic andductile.

According to an exemplary embodiment of the invention, a semi-flexiblePCB is provided with a semi-flexible portion having a dielectricmaterial with low Young modulus below 5 GPa and high elongation above3%. Conventionally, PCBs have been used for high bend radiusapplications only with estimated radius above 5 mm up to 5 cycle bendingrequirement. In contrast to this, according to an exemplary embodimentof the invention, it is possible to lower the bend radius down to 2 mmor less and/or to increase the bending endurance up to 100 cycles withbending condition of more than 5 mm.

Such a dielectric material at least in the semi-flexible portion mayhave an ultra-low Young modulus below 5 GPa (preferably below 1 GPa) andhigh elongation above 3% (preferably above 4%). To produce the ultra-lowmodulus materials in terms of a PCB manufacturing process, it has turnedout advantageous to specifically adjust a hot press lamination process.

In particular, the material selection and manufacturing process ofexemplary embodiments of the invention can be applied in particular tocomponent carriers with 1 to 10, in particular 4 to 10, bending layersso that at least one of the bending layers is prepreg with glassreinforcement. Preferably, at least the outermost layer (considering thebend direction) can be made of an RCC (resin coated copper) materialwith low Young modulus below 5 GPa and high elongation above 3%. Bytaking this measure, it may be possible to improve the bendingperformance in terms on small-flex width, high bending angle andincreased maximum number of bending times of a semi-flex componentcarrier. As a result, it may be possible to achieve a reliable bendingcapability of a semi-flex component carrier. In particular, it may bepossible to introduce such a low modulus material into semi-flex PCBtechnology, and to reduce the manufacturing effort over conventionalrigid-flex PCB technology. Synergistically, exemplary embodiments of theinvention may promote electrical and mechanical miniaturization.Furthermore, exemplary embodiments of the invention may extend bendingto install semi-flex application and are properly compatible with massproduction on an industrial scale.

In terms of said dielectric material's Young modulus, at least oneelectrically insulating layer extending into a semi-flexible portion maybe made of low modulus dielectric material below 5 GPa, in particularbelow 2 GPa.

What concerns material elongation, the at least one electricallyinsulating layer structure extending into the semi-flexible portion maybe made of ultra-high elongation dielectric material about 3%, inparticular by 5%, preferably above 10%.

Said material's coefficient of thermal expansion (CTE) is preferablybelow 150 ppm/K at room temperature. The CTE value is however preferablylarger than 30 ppm/K.

In terms of flex area configuration, said low Young modulus (below 5GPa) and high elongation (above 3%) material can, for example, haveeither of the following configurations:

a. said layer may be arranged on the outer layer of the stack in thesemi-flexible portionb. said layer may be arranged in the center of the stack in thesemi-flexible portion.

In particular, the semi-flexible portion can have a layer count in arange between 1 and 8 layers, in particular between 4 and 8 layers.

What concerns the mechanical bend design, it is preferred that the flexarea length is longer than 1 mm. The bend angle can be, for instance, ina range between 0° and 180°.

Highly advantageously, the described architecture, both in the rigidportion and the semi-flexible portion, is compatible with the embeddingof components, in particular large die embedding.

Exemplary embodiments of the invention may be implemented in allsemi-flex component carriers and can be used to overcome conventionalshortcomings of rigid-flex technology.

FIG. 1 to FIG. 5 illustrate cross-sectional views of structures obtainedduring manufacturing a semi-flex component carrier 100, shown in FIG. 5,according to an exemplary embodiment of the invention.

Referring to FIG. 1, base materials for the manufacturing process areshown. In particular, a low-flow or no-flow uncured layer structure 118is sandwiched between a first multilayer structure 120 and a secondmultilayer structure 122.

Uncured layer structure 118 has not yet been fully cured bycross-linking its resin material by the application of pressure and/orheat. Thus, applying pressure and/or heat may re-melt the not yet curedresin material of the uncured layer structure 118 which is thereforecapable of providing an adhesion function with connected layerstructures upon triggering the curing process. For instance, the uncuredlayer structure 118 may be made of a low-flow or no-flow prepreg (i.e.resin, such as epoxy resin, comprising reinforcing particles, such asglass fibers). Such a low-flow or no-flow prepreg has the property thatit will only flow to a very limited extent, if at all, into adjacentgaps during curing (which may be triggered by pressure and/or heating).Also, liquid dielectrics may be used.

The first multilayer structure 120 may be a fully cured core, forinstance consisting of FR4 material as electrically insulating layerstructure 106 covered on both opposing main surfaces thereof with arespective copper foil as electrically conductive layer structure 104.

The second multilayer structure 122 may, for example, be a resin coatedcopper (RCC) foil. For example, the second multilayer structure 122 maybe composed of an electrically conductive layer structure 104 (forinstance a copper foil) and an electrically insulating layer structure106′ on the electrically conductive layer structure 104 and formed onthe basis of an ultra-low Young modulus material with a high elongation.More precisely, the value of the Young modulus of electricallyinsulating layer structure 106′ may be less than 5 GPa, and preferablyless than 1 GPa. In other words, the material of electrically insulatinglayer structure 106′ may be highly elastic. Furthermore, the material ofthe electrically insulating layer structure 106′ may have a highelongation of at least 3%, preferably at least 4%. As a result, theelectrically insulating layer structure 106′ may be highly ductile. Tofurther promote bendability of electrically insulating layer structure106′, it may be free of glass cloth or other reinforcing particles.Thus, highly advantageously, the uppermost electrically insulating layerstructure 106′ may comprise a material having an elongation of largerthan 4% and a Young modulus of less than 1 GPa. For instance, saidelectrically insulating layer structure 106′ comprises epoxyderivatives, in particular Ajinomoto Build-up Film® or specificallyconfigured epoxy resin. Preferably, said electrically insulating layerstructure 106′ is free of glass cloth, for instance consists of resinonly. The material of said electrically insulating layer structure 106′may have a coefficient of thermal expansion of at least 30 ppm/K, butless than 150 ppm/K. All mentioned parameters refer to a temperature of300 K. The electrically insulating layer structure 106′ may be fullycured to simplify cavity formation (compare description of FIG. 4), butmay also be at least partially uncured in another embodiment of themanufacturing method.

A thickness of the electrically insulating layer structure 106 of thefirst multilayer structure 120 may be larger than a thickness of theelectrically insulating layer structure 106′ of the second multilayerstructure 122.

Referring to FIG. 2, preparation of the base materials shown in FIG. 1before lay-up is illustrated.

As shown, the first multilayer structure 120 is provided with a steppedprofile with a central protrusion 125 surrounded by a lateral base 126and an indentation 140 in the base 126. This can be accomplished bypatterning the upper electrically conductive layer structure 104 of thefirst multilayer structure 120. The indentation 140 may be formed as agroove or a channel in the electrically insulating layer structure 106of the first multilayer structure 120 along a pre-determined transitionline. The indentation 140 may be formed to laterally surround theprotrusion 125 and will later serve for defining formation of a cavity130. For forming the indentation 140, it is possible to remove the FR4material of the electrically insulating layer structure 106 of the firstmultilayer structure 120 at one side except the region defined by thecopper of protrusion 125 in the later bending area of the semi-flexcomponent carrier 100 to be manufactured. Dielectric material may bemechanically, physically or chemically removed, copper may be etched. Itis also possible to form the indentation 140 by carrying out a pre-deepmilling procedure in the thick FR4 material of the electricallyinsulating layer structure 106 of the first multilayer structure 120.

Furthermore, the low-flow or no-flow uncured layer structure 118 ispatterned to form a central recess 128 matching to the protrusion 125.The central recess 128 is positioned and dimensioned to accommodate theprotrusion 125 and to be aligned with the indentation 140. Formation ofthe central recess 128 in the low-flow or no-flow uncured layerstructure 118 may be accomplished, for example, by milling, punching orlaser cutting the low-flow or no-flow uncured layer structure 118selectively. Thus, the upper copper foil of the first multilayerstructure 120 is patterned for forming the protrusion 125 providing aform closure with the recessed at least partially uncured low-flow orno-flow layer structure 118. The thickness of the upper electricallyconductive layer structure 104 of the first multilayer structure 120forming the protrusion 125 on the one hand and the thickness of the atleast partially uncured low-flow or no-flow prepreg layer structure 118may be the same or may be similar so as to obtain a vertical alignment.

The indentations 140 or slits serve for spatially delimiting the cavity130 to be formed. Descriptively speaking, the indentations 140 support amilling tool 117 (see FIG. 4) to properly spatially define asemi-flexible portion 110 of the semi-flex component carrier 100 to beformed. As can be taken from FIG. 2, a gap “d” is defined between aninterior side wall of the uncured low-flow or no-flow prepreg layerstructure 118 and an adjacent side wall of the upper electricallyconductive layer structure 104 of the first multilayer structure 120.Preferably, the dimension of gap “d” may be selected to be identical orsubstantially identical to a horizontal extension “b” of the indentation140. More precisely, it should be mentioned that gap “d” denotes thecorresponding dimension after connection of the shown layers (whichmeans that, during cutting, the flow of material during laminationshould be taken into account). More specifically, the exterior side wallof the indentation 140 may be in alignment with the interior side wallof the uncured low-flow or no-flow prepreg layer structure 118.Furthermore, the interior side wall of the indentation 140 may be inalignment with the sidewall of the upper electrically conductive layerstructure 104 of the first fully cured multilayer structure 120.

Referring to FIG. 3, an interconnected stack 102 is formed by connectingthe low-flow or no-flow uncured layer structure 118 between the firstmultilayer structure 120 and the second multilayer structure 122 bylamination, i.e. the application of pressure and/or heat. As a result,the electrically insulating uncured material of the low-flow or no-flowuncured layer structure 118 may re-melt, carry out cross-linking and maysubsequently re-solidify. As a result, an adhesion force is createdexclusively at the direct interfaces between layer structure 118 and thedirectly connected layer structures 120, 122. Since layer structure 118is made of low-flow or no-flow material, this material will not flow orwill not flow significantly into indentation 140, thereby advantageouslykeeping indentation 140 open and thereby simplifying the formation ofthe cavity 130 in a later process. For ensuring that material of layerstructure 118 does not completely fill indentation 140 duringlamination, the recess 128 formed in layer structure 118 according toFIG. 2 may be made sufficiently large.

As can be taken from the cross-sectional view of FIG. 3, the recesseduncured electrically insulating layer structure 118 is configured sothat prepreg material is safely prevented from flowing into theindentations 140 during lamination. The distance or gap “d” may bemaintained unfilled with the previously uncured (low-flow or) no-flowprepreg layer structure 118 being cured during lamination, since inparticular no-flow prepreg has the property of performing substantiallyno-flow during curing. However, the distance or gap “d” may bealternatively partially or entirely filled with the previously uncuredlow-flow (or no-flow) prepreg layer structure 118 being cured duringlamination, since in particular low-flow prepreg has the property ofperforming a certain (however relatively small) flow during curing.

Referring to FIG. 4, material is removed to thereby form a cavity 130 inthe stack 102 to delimit a semi-flexible portion 110 defined by thecavity 130 from two opposing rigid portions 108 (compare FIG. 5). Thesemi-flexible portion 110 corresponds to the portion of the cavity 130,whereas the rigid portions 108 correspond to thicker portions of thelaminated stack 102 around the cavity 130. Forming the cavity 130 may beaccomplished by removing material of the stack 102 by milling using amilling tool 117 (indicated schematically in FIG. 4). During themilling, the lateral position of the milling tool 117 may be controlledso that steps (see reference numeral 114 in FIG. 5) are defined. Thecorresponding spatial adjustability of the position of the milling tool117 is indicated by double arrows 164. Forming the cavity 130 may hencebe accomplished by removing material substantially laterally inside ofthe indentation 140 by cutting the stack 102, from a bottom sidethereof, substantially around the indentation 140. Thereafter, anon-adhering piece 132 of material surrounded by a corresponding cuttingline may be simply taken out of the stack 102, thereby obtaining thecavity 130. The piece 132 does not adhere circumferentially, since it iscircumferentially separated from the rest of the layer structures shownin FIG. 3 by milling. Furthermore, the piece 132 does not adhere at itstop surface which corresponds to the upper main surface of theprotrusion 125, since it does not comprise material of the (meanwhilecured) layer structure 118. Since the upper surface of the separationarea delimiting the piece 132 is formed by the interface between theupper electrically conductive layer structure 104 of the former firstmultilayer structure 120 and the electrically insulating layer structure106′ of the former second multilayer structure 122, the lamination hasnot caused an adhesion there.

As further shown in FIG. 4, a finishing procedure may be carried out bydepositing a first solder mask 171 on a portion of exposed electricallyconductive surfaces of the obtained layer structure in the rigidportions 108, while a second solder mask 173 may be formed on an upperportion of exposed electrically conductive surfaces of the obtainedlayer structure in the bending portion or semi-flexible portion 110.

After having taken out the piece 132 and after formation of the soldermasks 171, 173, the semi-flex component carrier 100 shown in FIG. 5 isobtained.

Referring to FIG. 5, the PCB manufacturing process may be finished bydefining circumferential step 114 by correspondingly positioning themilling tool 117 for removing material of the stack 102 for forming thecavity 130 and by taking out the correspondingly formed piece 132. Thestep 114 is formed in a transition portion between the rigid portion 108and the semi-flexible portion 110 in a corner of the cavity 130. Aslight flow of low-flow prepreg or no flow prepreg may occur. As aresult, the semi-flex component carrier 100 shown in FIG. 5 is obtained.

The semi-flex component carrier 100 is here embodied as a printedcircuit board (PCB) and comprises laminated stack 102 composed ofelectrically conductive layer structures 104 and electrically insulatinglayer structures 106, 106′. For example, the electrically conductivelayer structures 104 may comprise patterned copper foils and verticalthrough connections, for example copper filled laser vias. Theelectrically insulating layer structure 106 may comprise a resin (suchas epoxy resin) and reinforcing particles therein (for instance glassfibers or glass spheres). For instance, the electrically insulatinglayer structure 106 may be made of prepreg or FR4. Electricallyinsulating layer structure 106′ may be an epoxy resin layer withoutglass fibers and with lower Young modulus and higher elongation than thematerial of electrically insulating layer structure 106. The layerstructures 104, 106, 106′ may be connected by lamination, i.e. theapplication of pressure and/or heat.

As shown, said electrically insulating layer structure 106′ with lowYoung modulus and high elongation extents over the entire semi-flexibleportion 110 and the entire at least one rigid portion 108. Saidelectrically insulating layer structure 106′ is the outermostelectrically insulating layer structure of the laminated stack 102. Theoutermost electrically insulating layer structure 106′ is particularlyprone to crack formation during bending. Thus, configuring saidoutermost layer structure 106′ from a low Young modulus and highelongation material, elongation stress may be suppressed mostefficiently. The semi-flexible portion 110 may have a horizontal lengthl of at least 1 mm, for instance 2 mm.

In particular in bending areas corresponding to interface regions 195between the semi-flexible portion 110 and the rigid portions 108, therisk of crack formation during bending of the semi-flexible portion 110is particularly pronounced. However, in view of the low Young modulusand high elongation of the soft and elastic, more ductile than brittle,electrically insulating layer structure 106′, mechanical durability inparticular in the interface regions 195 may be significantly improved.

The semi-flex component carrier 100 according to FIG. 5 comprises theexterior rigid portions 108, the central semi-flexible portion 110 andthe cavity 130 delimiting the semi-flexible portion 110 from the rigidportions 108. In other words, the semi-flexible portion 110 is arrangedbetween or is enclosed by different rigid portions 108. The step 114 ina transition portion between the rigid portions 108 and thesemi-flexible portion 110 in corners of the cavity 130 improves themechanical integrity. While the rigid portions 108 and the semi-flexibleportion 110 comprise substantially the same materials, the rigid portion108 is rendered rigid by providing it with a larger vertical thicknessthan the semi-flexible portion 110. The latter is rendered flexible inview of its small thickness and the material selection of electricallyinsulating layer structure 106′. As can be taken from FIG. 5 as well,the rigid portions 108 and the semi-flexible portion 110 share commoncontinuous electrically insulating layer structure 106′ whichcorresponds to the original electrically insulating layer structure 106′of the second multilayer structure 122.

As shown in FIG. 5, the cavity 130 has a rectangular cross-section withcorners in which the step 114 is formed as a convex protrusion 124. Moreprecisely, the step 114 is formed by the meanwhile cured low-flowprepreg layer structure 118 in the transition portion. The presence ofthe steps 114 has a highly positive impact on the mechanical integrityof the semi-flex component carrier 100 even in the presence of bendingforces or other tension forces exerted to the semi-flex componentcarrier 100 during operation or handling. As can be taken from referencenumerals 153, 155, an exerted force (see reference numeral 153) may bemanipulated or redirected by the step 114 (see reference numeral 155).Whichever theoretical explanation may be given, it has turned out thatthe presence of the step 114 improves the mechanical integrity of thesemi-flex component carrier 100.

In the corner region or transition region of the semi-flex componentcarrier 100, the exerted force may be maximum. However, the breakageforce in the corner region may be smaller in the absence of the step114. By the presence of the step 114, the force limit of failure can beincreased.

FIG. 6 is a cross-sectional view of a portion of a semi-flex componentcarrier 100 according to another exemplary embodiment of the invention.

According to FIG. 6, said electrically insulating layer structure 106′with low Young modulus and high elongation is the outermost electricallyinsulating layer structure 106 of the stack 102. Optionally, one or twofurther electrically insulating layer structure 106″, 106′″ in thesemi-flexible portion 110 being located in an interior of the stack 102may also be provided with low Young modulus of less than 5 GPa or evenless than 1 GPa and high elongation of more than 3% or even more than4%. This further improves the bendability characteristic of thecomponent carrier 100.

FIG. 7 illustrates a three-dimensional view of a semi-flex componentcarrier 100 according to still another exemplary embodiment of theinvention. Said electrically insulating layer structure 106′ formingpart of the semi-flexible portion 110 may be bent about a freelydefinable bending angle R in a range between 0° in 180°, in the presentembodiment approximately 90°. Since the outermost portion 111 of thesemi-flexible portion 110 is most prone to damage during bending,arranging the electrically insulating layer structure 106′ with lowYoung modulus and high elongation at the side of said outermost portion111 it is of utmost advantage.

FIG. 8 illustrates a design of a semi-flex component carrier 100according to a further exemplary embodiment of the invention. Thenumbers in FIG. 8 illustrate the respective thickness of the respectivelayer structure in micrometers. As shown, all of the layer structures104, 106, 106′ of the semi-flexible portion 110 also extend along the atleast one rigid portion 108. More specifically, all of the layerstructures 104, 106 are made of the same material and have the samethickness in the semi-flexible portion 110 and in the at least one rigidportion 108.

As shown, the rigid portion 108 comprises an alternating sequence of sixelectrically conductive layer structures 104 and five electricallyinsulating layer structures 106. On top and on bottom of laminated stack102, a respective solder resist 171, 173 is formed. While a standardsolder mask may be used in the rigid portion 108 (compare referencenumeral 171), a flexible solder mask ink may be implemented in thesemi-flexible portion 110 (compare reference numeral 173). The uppermostelectrically insulating layer structure 106′ is configured as anepoxy-based material without glass cloth and having said low Youngmodulus and high elongation. Said electrically insulating layerstructure 106′ may be formed on the basis of an ultra-low modulus RCC(resin coated copper) foil. It is for instance also possible toconfigure the lowermost electrically insulating layer structure 106′ inthe rigid portion 108 as ultra-low modulus RCC-based layer. All otherelectrically insulating layer structures 106 may be made of prepregcomprising glass fibers or glass spheres as reinforcing particles. Thethickest and most central electrically insulating layer structure 106may be a core. The electrically conductive layer structures 104 arepatterned or continuous copper layers (for instance formed by acombination of base copper and plated copper). In addition, verticalthrough connections (in particular copper filled laser vias) areprovided forming part of the electrically conductive layer structures104, but being located exclusively in the rigid portion 108.

FIG. 9 illustrates a cross-sectional view of a semi-flex componentcarrier 100 according to still another exemplary embodiment of theinvention.

In the embodiment of FIG. 9, the semi-flexible portion 110 is formed asa central portion of the stack 102. The full thickness portion of thestack 102 constitutes the rigid portion 108. Material of the stack 102is removed from both opposing main surfaces in the semi-flexible region110 so that two cavities 130 at opposing main surfaces of the componentcarrier 100 are formed, thereby delimiting the semi-flexible portion110.

Highly advantageously, it is possible to embed one or more components132 (such as semiconductor chips) in the semi-flex component carrier100. In the shown embodiment, one component 132 is embedded in a centralcore 191 of the rigid portion 108. Another component 132 is embedded inthe central core 191 in the semi-flexible portion 110.

The component carrier 100 according to FIG. 9 also comprises acage-shaped or shell-shaped locally elastic mechanical buffer structure144 selectively surrounding the embedded components 132. The mechanicalbuffer structure 144 may be an epoxy resin layer without glass fibersand with lower Young modulus (for instance below 1 GPa) and higherelongation (for instance above 5%) than the material of the remainingelectrically insulating layer structures 106, for instance withexception of electrically insulating layer structure 106′ only. Asshown, said mechanical buffer structures 144 with low Young modulus andhigh elongation surround substantially the entire embedded components132 (for instance semiconductor chips), with the exception of contactvias (not shown) electrically contacting the component 132 with theelectrically conductive layer structures 104 and/or an environment ofthe component carrier 100. More specifically, the mechanical bufferstructure 144 covers horizontal surface portions as well as verticalsidewalls of the component 132. The mechanical buffer structure 144 isshaped as a shell surrounding substantially the entire component 132,with the only exception of said one or more vias (not shown) contactingone or more pads (not shown) on a horizontal main surface of thecomponent 132. Said mechanical buffer structure 144 encapsulatescomponent 132 which is particularly prone to crack formation duringbending of the semi-flex component carrier 100. Thus, configuring saidmechanical buffer structure 144 from a low Young modulus and highelongation material, elongation stress may be suppressed mostefficiently. Descriptively speaking, an elastic and ductileencapsulation of the component 132 embedded in the rigid portion 108 mayreliably protect the sensitive semiconductor component 132 againstdamage when bending the semi-flex component carrier 100 about bendingpoint(s) 148. Apart from the selective individual change of the materialcomposition directly around the component 132 by providing mechanicalbuffer structure 144, the rest of the stack 102 may be made ofconventional and well available materials, with the exception ofelectrically insulating layer structure 106′.

As can be taken from FIG. 9 as well, a vertical extension range L of thecomponents 132 does not encompass a vertical level of bending points 148between the shown rigid portion 108 and the shown semi-flexible portion110. Furthermore, a stress propagation inhibiting barrier 150 in form ofa plurality of vertically stacked vias filled with electricallyconductive material such as copper in an interface region between theillustrated rigid region 108 and the illustrated semi-flexible portion110 inhibits stress propagation between the semi-flexible portion 110and the rigid region 108 and up to the components 132 during bending.Said measures, i.e. a vertical displacement of the component 132 withrespect to the bending points 148 and the provision of a stresspropagation inhibiting structure 150, additionally contribute to thereliable protection of the embedded components 132 from damage duringbending.

As shown in FIG. 9 as well, a transition region between thesemi-flexible portion 110 and the rigid portion 108 has slantedsidewalls 154, both at the top side and on a bottom side. This furthercontributes to the protection of the component carrier 100 againstdamage during bending.

FIG. 10 illustrates a cross-sectional view of a semi-flex componentcarrier 100 according to yet another exemplary embodiment of theinvention.

The semi-flex component 100 shown in FIG. 10 corresponds to thearchitecture described above referring to FIG. 6, but additionally hascomponents 132 embedded in both the rigid portion 108 and thesemi-flexible portion 110 which extend up to an upper main surface ofthe component carrier 100.

It has turned out surprisingly that the embedding of a respectivecomponent 132 in a semi-flexible region 110 comprising one or twoelectrically insulating layer structures 106′ with low Young modulus andhigh elongation has no significant negative impact on the bendabilityand on the risk of crack formation in the semi-flexible portion 110.

FIG. 11 illustrates schematically a polymer with different functionalsections 112, 115, 116 which may be used for forming the electricallyinsulating layer structure 106′ according to an exemplary embodiment ofthe invention.

The illustrated polymer has a central flexible segment 112 between areactive segment 115 on one side and a hard segment 116 on the opposingother side. The hard segment 116 may be configured to have a hightemperature resistance. The flexible segment 112 promotes low warpageand serves for a relaxation on internal stress. The reactive segment 115may be configured for reacting with epoxy resin to thereby form largercompounds.

It should be noted that the term “comprising” does not exclude otherelements or steps and the article “a” or “an” does not exclude aplurality. Also, elements described in association with differentembodiments may be combined.

Implementation of the invention is not limited to the preferredembodiments shown in the figures and described above. Instead, amultiplicity of variants is possible which use the solutions shown andthe principles according to the invention even in the case offundamentally different embodiments.

1.-27. (canceled)
 28. A semi-flex component carrier, comprising: astack, in particular a laminated stack, comprising at least oneelectrically insulating layer structure, at least one electricallyconductive layer structure and a stress propagation inhibiting barrier,wherein the stack defines at least one rigid portion and at least onesemi-flexible portion; the stress propagation inhibiting barriercomprising a plurality of stacked vias filled at least partially withelectrically conductive material, in an interface region between the atleast one rigid portion and the at least one semi-flexible portion andconfigured to inhibit stress propagation between the at least one rigidportion and the at least one semi-flexible portion during bending. 29.The component carrier according to claim 28, further comprising: acentral core of the stack, wherein at least one of the plurality of viasextends through the central core.
 30. The component carrier according toclaim 28, wherein the plurality of stacked vias is arranged in the atleast one rigid portion adjacent to the at least one semi-flexibleportion.
 31. The component carrier according to claim 28, furthercomprising: a central core of the stack, wherein a first via of theplurality of vias extends through the central core; a second via of theplurality of vias extends through the at least one electricallyinsulating layer structure of the stack; the first and second vias arevertically stacked and aligned.
 32. The component carrier according toclaim 31, wherein first and second vias are arranged in the at least onerigid portion adjacent to the at least one semi-flexible portion. 33.The component carrier according to claim 31, wherein an electricallyconductive layer structure is arranged between the first and secondvias.
 34. The component carrier according to claim 28, wherein, in across section of the component carrier, the plurality of stacked vias dovertically not extend beyond an outer surface of the at least onesemi-flexible portion.
 35. The component carrier according to claim 31,wherein, in a cross section of the component carrier, the plurality ofstacked vias do vertically not extend beyond an outer surface of the atleast one semi-flexible portion.
 36. The component carrier according toclaim 28, further comprising a component embedded in the stack adjacentto at least one via of the plurality of stacked vias.
 37. The componentcarrier according to claim 28, wherein the at least one of the at leastone electrically insulating layer structure forming at least part of thesemi-flexible portion comprises at least one of the following features:it comprises a material having an elongation of larger than 3% and aYoung modulus of less than 5 GPa; it comprises or consists of at leastone of an epoxy resin, and epoxy derivatives, in particular Ajinomoto®Build-up Film; it is free of glass cloth, in particular is free ofreinforcing particles embedded in a resin matrix; it extends over the atleast one semi-flexible portion and over the at least one rigid portion;it has an elongation of larger than 3% and a Young modulus of less than5 Gpa comprises an outermost electrically insulating layer structure ofthe stack; it has an elongation of larger than 3% and a Young modulus ofless than 5 Gpa comprises an interior one, in particular a central one,of the electrically insulating layer structures of the stack.
 38. Thecomponent carrier according to claim 28, wherein all of the layerstructures of the semi-flexible portion also extend along the at leastone rigid portion, wherein in particular all of said layer structuresare made of the same material and/or have the same thickness in thesemi-flexible portion and in the at least one rigid portion.
 39. Thecomponent carrier according to claim 28, further comprising: at leastone step at an interface between the semi-flexible portion and the atleast one rigid portion.
 40. The component carrier according to claim28, wherein the component carrier has the semi-flexible portion betweentwo opposing rigid portions.
 41. The component carrier according toclaim 28, wherein the at least one semi-flexible portion has a smallernumber of layer structures and/or has a smaller thickness than the atleast one rigid portion.
 42. The component carrier according to claim28, wherein the at least one of the at least one electrically insulatinglayer structure forming at least part of the semi-flexible portioncomprises a polymer having a flexible segment between a reactive segmentand a hard segment.
 43. The component carrier according to claim 42,further comprising: at least one of the following features: wherein thehard segment has a high temperature resistance; wherein the flexiblesegment shows low warpage and relaxation on internal stress; wherein thereactive segment is configured for reacting with epoxy resin.
 44. Thecomponent carrier according to claim 28, wherein the at least one of theat least one electrically insulating layer structure forming at leastpart of the semi-flexible portion comprises at least one of thefollowing features: it has a Young modulus of less than 2 GPa, inparticular less than 1 GPa; it has an elongation of larger than 4%, inparticular larger than 5%, more particularly larger than 10%, and inparticular smaller than 20%; it has a coefficient of thermal expansionof less than 150 ppm/K at a temperature of 300 K, and in particular hasa coefficient of thermal expansion of at least 30 ppm/K at a temperatureof 300 K.
 45. The component carrier according to claim 28, wherein theflexible portion has a horizontal length of at least 1 mm.
 46. Thecomponent carrier according to claim 28, wherein the semi-flexibleportion is bent about a bending angle in a range between 0° in 180°. 47.The component carrier according to claim 28, further comprising: acomponent embedded in the stack, in particular in a central core of thestack.
 48. The component carrier according to claim 28, furthercomprising: a mechanical buffer structure surrounding at least part ofthe component and having a lower value of the Young modulus than otherelectrically insulating material of the stack.
 49. The component carrieraccording to claim 48, wherein the mechanical buffer structure comprisesa material having an elongation of larger than 3%, in particular largerthan 5%, and a Young modulus of less than 5 GPa, in particular less than1 GPa.
 50. The component carrier according to claim 28, wherein avertical extension range of the component does not encompass a verticallevel of at least one bending point between the at least one rigidportion and the at least one semi-flexible portion.
 51. The componentcarrier according to claim 28, wherein a transition region between theat least one rigid portion and the at least one semi-flexible portionhas at least one slanted sidewall.
 52. The component carrier accordingto claim 28, further comprising at least one of the following features:at least one component surface mounted on and/or embedded in the stack,wherein the at least one component is in particular selected from agroup consisting of an electronic component, an electricallynon-conductive and/or electrically conductive inlay, a heat transferunit, a light guiding element, an energy harvesting unit, an activeelectronic component, a passive electronic component, an electronicchip, a storage device, a filter, an integrated circuit, a signalprocessing component, a power management component, an optoelectronicinterface element, a voltage converter, a cryptographic component, atransmitter and/or receiver, an electromechanical transducer, anactuator, a microelectromechanical system, a microprocessor, acapacitor, a resistor, an inductance, an accumulator, a switch, acamera, an antenna, a magnetic element, a further component carrier, anda logic chip; wherein the at least one electrically conductive layerstructure comprises at least one of the group consisting of copper,aluminum, nickel, silver, gold, palladium, and tungsten, any of thementioned materials being optionally coated with supra-conductivematerial such as graphene; wherein at least one of the at least oneelectrically insulating layer structure comprises at least one of thegroup consisting of resin, in particular reinforced or non-reinforcedresin, for instance epoxy resin or Bismaleimide-Triazine resin, FR-4,FR-5, cyanate ester, polyphenylene derivate, glass, prepreg material,epoxy-based Build-Up Film, polytetrafluoroethylene, a ceramic, and ametal oxide; wherein the component carrier is shaped as a plate; whereinthe component carrier is configured as one of the group consisting of aprinted circuit board, and a substrate; wherein the component carrier isconfigured as a laminate-type component carrier.
 53. A method ofmanufacturing a semi-flex component carrier, wherein the methodcomprises: providing, in particular laminating, a stack comprising atleast one electrically insulating layer structure, at least oneelectrically conductive layer structure and a stress propagationinhibiting barrier, wherein the stack defines at least one rigid portionand at least one semi-flexible portion; wherein the stress propagationinhibiting barrier comprising a plurality of stacked vias filled atleast partially with electrically conductive material, in an interfaceregion between the at least one rigid portion and the at least onesemi-flexible portion and configured to inhibit stress propagationbetween the at least one rigid portion and the at least onesemi-flexible portion during bending.
 54. The method according to claim53, wherein said at least one electrically insulating layer structure islaminated as part of a resin coated copper foil to the stack, inparticular both in the semi-flexible portion and in the at least onerigid portion.